In the small-sized image pickup apparatus of a digital camera or of a camera built in a cell-phone, image quality deterioration caused by image shake has become a problem, as the apparatus is downsized more and more, and mounting of an image shake correction section is becoming indispensable. Further, a small-sized image pickup apparatus installed in a digital camera or in a cell-phone is required to be smaller in size, to be lower in cost and to have higher functions at the same time. The higher functions mean functions such as “autofocus function”, “automatic exposure control function” and “image shake correction function” which have been realized on a digital camera. As actuators for realizing the aforesaid functions in the conventional digital camera, an actuator optimum for each function was developed and adopted independently.
A principle of the image shake correction will be explained as follows, referring to FIG. 11 which is a schematic diagram for illustrating the principle of the image shake correction.
In FIG. 11, image pickup apparatus 1 is provided with image pickup optical system 211 composed of lens 211 and lens 212, image pickup device 162 and image shake detection section 301. When optical axis 200 of image pickup optical system 211 is deflected by image shake in the vertical direction (hereinafter referred to as P direction: meaning of Pitch), the horizontal direction (hereinafter referred to as Y direction: meaning of Yaw) or in the direction of composition of the vertical and horizontal directions, the image shake detection section 301 detects the direction and an amount of the deflection, and the image pickup device 162 or the lens 211b that is a part of the image pickup optical system 211 is moved in the P direction, Y direction or in both directions of P and Y to cancel the image shake, and a subject image on the image pickup device is kept to be fixed constantly. The foregoing is a principle of the image shake correction.
As a conventional image shake correction, there have been suggested a mechanism (for example, see Japanese Laid-Open Patent Publication No. 2003-110919) to correct image shake by moving an image pickup device by the use of a linear actuator (SIDM: Smooth Impact Drive Mechanism) wherein a piezoelectric element, for example, serves as a driving source and a mechanism (for example, see Japanese Laid-Open Patent Publication No. 2001-194571) to correct image shake by moving a lens that is a part of the image pickup optical system with string-like shape-memory alloy (SMA: Shape Memory Alloys) that serves as a driving source. Further, there has been suggested that a driving section of a calibration device of an image pickup apparatus having a function of correcting image shake with a polymer actuator serving as a driving source (for example, see Japanese Laid-Open Patent Publication No. 2005-330457).
Further, for example, a voice coil motor using electromagnetic force and a linear actuator using a piezoelectric element as a driving source (SIDM: Smooth Impact Drive Mechanism) are used for the “autofocus function”, and a diaphragm mechanism employing a galvanometer is used for the “automatic exposure control function”.
As a mounting method of an actuator for the foregoing, there has been suggested a camera module carried by a cell-phone, for example, wherein the actuator is formed on a base plate of an image sensor for achieving downsizing (for example, see Japanese Laid-Open Patent Publication No. 2003-204470). There has further been suggested one wherein a supporting mechanism for focusing and that for tilting are formed integrally in a lens holder of an optical pickup device (for example, see Japanese Laid-Open Patent Publication No. 10-106013).
However, a suggestion of Japanese Laid-Open Patent Publication No. 2003-204470 is limited to the “function of correcting image shake”, and a separate actuator needs to be provided for the “autofocus function”. In the suggestion of Japanese Laid-Open Patent Publication No. 10-106013), an actuator for focusing and an actuator for tilting are used separately, although the supporting mechanism is integrated, and there are problems in terms of a size, a simplicity of assembly and adjustment and cost in mounting plural different actuators on an ultracompact equipment such as a cell-phone, even when each actuator is downsized.
Recently, on the other hand, a polymer actuator is attracting public attention on the points that it generates great force, it is light in weight, it is noiseless, it can be driven by low voltage, and it can be formed to be any shape in forming because it is resin.
However, in the method of Japanese Laid-Open Patent Publication No. 2003-110919, spaces are required on the circumference and on the rear side of an image pickup device for arranging SIDM, and when driving in at least two axes are required as in the case of image shake correction, one SIDM must drive including the other SIDM for at least one direction because SIDM is a uniaxial driving element, and the total apparatus tends to be large in size and heavy in weight because an object to be driven becomes heavy and SIDM having large driving force is required.
Further, in the method of Japanese Laid-Open Patent Publication No. 2001-194571, SMA that is large to a certain extent is required to increase an amount of displacement, because an amount of displacement of SMA is relatively small, and a space for arranging SMA tends to be large. In addition, the speed of response of SMA is not so high because SMA is controlled by thermal response, resulting in an aspect that SMA lacks high responsiveness.
However, in the suggestion of Japanese Laid-Open Patent Publication No. 2005-330457, neither specific means nor specific method is suggested, except a description that a polymer actuator is suitable for a driving portion of a calibration device of an image pickup apparatus having a function of correcting image shake.